Mach principle, 2

However, general relativity predicts and experiments confirm that gravitational waves do exist: the relevant observations were awarded by the 1993 physics Nobel prize, too. The waves are vibrations of the space itself. It means that the metric tensor remembers the information about the geometry – and curvature at each point, even in the empty space, something that Mach’s principle specifically wanted to prohibit.

Einstein had thought that Mach’s Principle was the way to go because it (also) made the universality encoded in the equivalence principle manifest. The equivalence principle says that all objects will be influenced equally – the same acceleration – by the whatever agent is causing gravity. Mach’s principle satisfies the criterion “totally” – it removes any field-like agent. Well, it’s going “too far” in this sense. Of course that Einstein was struggling for years to make Mach’s Principle compatible with the speed limit c – and GR is what eventually came out of it.

– Lubos Motl

2014.06.29 Sunday ACHK

Open Source MindOS

這段改編自 2010 年 4 月 10 日的對話。








那就即是話,你腦中的作業系統,是 Open Source 的 —— 容許別人修改。



— Me@2014.06.26


A stupid man’s report of what a clever man says is never accurate, because he unconsciously translates what he hears into something that he can understand.

— A History of Western Philosophy

— Bertrand Russell



2014.06.27 Friday (c) All rights reserved by ACHK


mantrax5 2 hours ago | link

“You know, one of the things that really hurt Apple was after I left John Sculley got a very serious disease. It’s the disease of thinking that a really great idea is 90% of the work. And if you just tell all these other people “here’s this great idea,” then of course they can go off and make it happen.

And the problem with that is that there’s just a tremendous amount of craftsmanship in between a great idea and a great product. And as you evolve that great idea, it changes and grows. It never comes out like it starts because you learn a lot more as you get into the subtleties of it. And you also find there are tremendous tradeoffs that you have to make. There are just certain things you can’t make electrons do. There are certain things you can’t make plastic do. Or glass do. Or factories do. Or robots do.

Designing a product is keeping five thousand things in your brain and fitting them all together in new and different ways to get what you want. And every day you discover something new that is a new problem or a new opportunity to fit these things together a little differently.

And it’s that process that is the magic.”

~ Steve Jobs

This is why Apple doesn’t make “vision” videos now, and it didn’t during the Jobs years. During the period they did, they had serious problems in shipping any of the visions they have shown the world.

Microsoft is a bit like that. They know where the world is going, and Bill Gates himself knew from the very start where the world is going (short of a brief period where he conveniently ignored the Internet will happen). But they thought the fact they knew, that they had this cool idea and projection of how things will happen was giving them enough advantage. Nope.

It’s risk-free to ship vision videos. They’re like free T-shirts. There’s infinite demand. But when it comes to shipping products based on them, most people can’t live with the compromises and risk-taking a real product requires in order to ship.

With a new product you can’t just look at the competition and confirm that what you have will work. You’re on your own. Do you have the guts?

— Hacker News

2014.06.24 Tuesday ACHK

The Lucifer Effect

Stanford prison experiment

Zimbardo’s book, The Lucifer Effect, gets its title from the metamorphosis of Lucifer into Satan. Though the Christian Scriptures do not make this claim, according to Christian legend, Lucifer was once God’s favorite angel until he challenged God’s authority and was cast into Hell with all the other fallen angels. Thus, Zimbardo derives this title to explain how good people turn evil. Zimbardo’s main assumption on why good people do awful things is due to situational influences and power given from authority.

The Lucifer Effect was written in response to his findings in the Stanford Prison Experiment. Zimbardo believes that personality characteristics could play a role in how violent or submissive actions are manifested. In the book, Zimbardo says that humans cannot be defined as “good” or “evil” because we have the ability to act as both especially at the hand of the situation. According to Zimbardo, “Good people can be induced, seduced, and initiated into behaving in evil ways. They can also be led to act in irrational, stupid, self-destructive, antisocial, and mindless ways when they are immersed in ‘total situations’ that impact human nature in ways that challenge our sense of the stability and consistency of individual personality, of character, and of morality.”

He also notes that we as humans wish to believe in unchanging goodness of people and our power to resist situational and external pressures and temptations. In chapter 12, “Investigating Social Dynamics: Power, Conformity, and Obedience”, Zimbardo discusses that peer pressure, the desire to be ‘cool’, the fear of rejection, and simply being a part of a group are the focal points to acting preposterous to your character.

In The Journal of the American Medical Association, Zimbardo’s situational perspective received support from other social situational experiments that demonstrated the same idea and concept. Almost ten years prior to the Stanford Prison Experiment (1971), Stanley Milgram conducted research on obedient behavior in 1965 that embraced situational forces. Milgram had “teachers” that delivered mock electric shocks to the “learner” for every wrong answer that was given in a multiple choice test. The teachers however did not know that the electric shocks weren’t real but still continued to deliver them to the learner. At the end of the experiment, 65% of men ages 20–50 complied fully up to the very last voltage. In the same room as the teacher, there was a “confederate” that kept tabs on the teacher and if they were delivering the shocks to each wrong answer. In the beginning of the study, participants signed a waiver that clearly explained the ability to opt-out of the experiment and not deliver the shocks. But with the surprising result rate of teachers who did continue to shock the learners, there was a situational force. The situational force that influenced the teachers to continue was the voice of the confederate egging them on by phrases such as, “I advise you to continue with this experiment” or “I am telling you to continue delivering the shocks” and the one that caught most teachers was “You must continue with the shocks.” Although the teachers knew that they could leave the experiment at any point in time, they still continued when they felt uncomfortable because of the confederate’s voice demanding to proceed.

Both Milgram and Zimbardo’s experiment tested situational forces on an individual. Both results concluded that irrational behavior compared to one’s character is plausible for any human because we have both tendencies in our nature.

— Wikipedia on Philip Zimbardo

2014.06.23 Monday ACHK


這段改編自 2010 年 4 月 10 日的對話。












— Me@2014.06.23


If you’re good at something, never do it for free.

— The Dark Knight


When you give a lot of importance to someone in your life, you lose your importance in their life.



2014.06.23 Monday (c) All rights reserved by ACHK

Mach principle

In theoretical physics, particularly in discussions of gravitation theories, a Mach principle is any of a class of principles which are more specific statements of Mach’s principle.

The broad notion is that “mass there influences inertia here”. Any statement which — though possibly far more specific than this — follows in this spirit may be classified as a “Mach principle”. The truth of these statements depends on the particular statement. (The truth also depends on the theory of gravity, though Einstein’s general relativity is the most frequently discussed theory.)


Hermann Bondi and Joseph Samuel have listed eleven distinct statements which can be called Mach principles, labelled by Mach0 through Mach10. Though their list is not necessarily exhaustive, it does give a flavor for the variety possible.

  • Mach0: The universe, as represented by the average motion of distant galaxies, does not appear to rotate relative to local inertial frames.
  • Mach1: Newton’s gravitational constant G is a dynamical field.
  • Mach2: An isolated body in otherwise empty space has no inertia.
  • Mach3: Local inertial frames are affected by the cosmic motion and distribution of matter.
  • Mach4: The universe is spatially closed.
  • Mach5: The total energy, angular and linear momentum of the universe are zero.
  • Mach6: Inertial mass is affected by the global distribution of matter.
  • Mach7: If you take away all matter, there is no more space.
  • Mach8: ( \Omega \ \stackrel{\mathrm{def}}{=}\ 4 \pi \rho G T^2 ) is a definite number, of order unity, where ( \rho ) is the mean density of matter in the universe, and T is the Hubble time.
  • Mach9: The theory contains no absolute elements.
  • Mach10: Overall rigid rotations and translations of a system are unobservable.

— Wikipedia on Mach principle

2014.06.22 Sunday ACHK

The Nice Guy Paradox, 2

Being a nice guy can be a problem, because “always being nice” gives no feedback and no directions. In effect, “always being nice” gives people an infinite number of choices. Remember,

choices ~ headaches

In other words, you should be nice as often as possible, but not always. Be angry when you have to.

— Me@2011.06.26

— Me@2014.06.22



2014.06.22 Sunday (c) All rights reserved by ACHK

Memory 5.4

這段改編自 2010 年 7 月 29 日的對話。


(HSY:會考剛放榜,我的物理成績只有 C。所以,學校當局很可能會,不容許我選修高考物理,而要我改為選修,例如,「數學與統計」科。





甲 = 你

乙 = 對方















— Me@2014.06.20



2014.06.21 Saturday (c) All rights reserved by ACHK

Charge, 2

Charge (physics), the susceptibility of a body to one of the fundamental forces

  • Color charge, a property of quarks and gluons, related to their strong interactions
  • Electric charge, a property which determines the electromagnetic interaction of subatomic particles
  • Magnetic charge, a property of theoretical magnetic monopoles

— Wikipedia on Charge

Symmetry and conservation

Conservation of momentum is a mathematical consequence of the homogeneity (shift symmetry) of space (position in space is the canonical conjugate quantity to momentum). That is, conservation of momentum is a consequence of the fact that the laws of physics do not depend on position; this is a special case of Noether’s theorem.

— Wikipedia on Momentum

Momentum is the Noether charge of translational invariance. As such, even fields as well as other things can have momentum, not just particles. However, in curved spacetime which isn’t asymptotically Minkowski, momentum isn’t defined at all.

2014.06.19 Thursday ACHK


這段改編自 2010 年 4 月 10 日的對話。










— Me@2014.06.17

2014.06.18 Wednesday (c) All rights reserved by ACHK

Time Reversal 2

Lessons from the Light, 5.3

They found that T is indeed violated.

All perfectly fine and glorious. The pet peeve only comes up in the sub-headline of the SLAC press release: “Time’s quantum arrow has a preferred direction, new analysis shows.” Colorful language rather than precise statement, to be sure, but colorful language that is extremely misleading.

“Time’s arrow,” in the sense that the phrase is conventionally used (by the kind of folks who would conventionally use such a phrase), refers to the myriad ways in which the past is different from the future in our macroscopic experiential reality. Entropy increases with time; … This new measurement in the B meson system — indeed, the entire phenomenon of T violation — has absolutely nothing to do with that arrow of time.

The reason is pretty simple to understand. The arrow of time centers on the concept of irreversibility — things happen in one direction of time but not the other. You can scramble eggs, but not unscramble them, etc. That’s not at all what’s going on in the B mesons. The oscillations between different types of meson happen perfectly well in both directions of time, just with ever-so-slightly different rates.

The particle-physics processes in question, in other words, are perfectly reversible. Information is not lost over time; you can figure out exactly what the quantum state used to be by knowing what it is now. (It’s “unitary,” to use the jargon word.) That’s utterly different from the macroscopic arrow of time.

— Time-Reversal Violation Is Not the “Arrow of Time”

— Sean Carroll

2014.06.13 Friday ACHK

The paradox of happiness solved

It is often said that we fail to attain pleasures if we deliberately seek them. This has been described variously, by many:

    Viktor Frankl in Man’s Search for Meaning:

    Happiness cannot be pursued; it must ensue, and it only does so as the unintended side effect of one’s personal dedication to a cause greater than oneself …

— Wikipedia on Paradox of hedonism

The paradox of happiness: 

If you do good work, you will feel happy.

However, if you do good work only because of the desire of getting happiness, you will not get it.


happiness ~ progress ~ self transcendence

do good work ~ keep going to the next levels


seeking happiness directly ~ focus on oneself ~ trapped at the same level

no progress ~ unhappiness

— Me@2011.06.22


~ 快


— Me@2014.06.13

2014.06.13 Friday (c) All rights reserved by ACHK

功夫傻瓜 3

中學實驗報告 4

這段改編自 2010 年 7 月 29 日的對話。













— Me@2014.06.11



2014.06.12 Thursday (c) All rights reserved by ACHK

Time Reversal

Lessons from the Light, 5.2

Note that among C, P, T, only T is an “antilinear operator” which means that

T | \lambda \psi \rangle = \lambda* T | \psi \rangle

including the asterisk which means complex conjugation (that’s the reason of the prefix, anti-). Various combinations of C, P, T are linear or antilinear depending on whether T is included.

Note that the complex conjugation is needed for the time reversal already in ordinary non-relativistic quantum mechanics because the complex conjugation is the only sensible way to change ( \exp(+ipx/\hbar) ) to ( \exp(-ipx/\hbar) ), i.e. to change the sign of the momentum p – and the velocity v = dx/dt – which is needed for particles to evolve backwards.

— BaBar directly measures time reversal violation

— Lubos Motl

2014.06.11 Wednesday ACHK


Presentation 基本原理 2


~ fuse

~ draw together

confuse ~ con + fuse

To avoid confusion, say only one point at a time. Don’t try to fuse several ideas at the same time, intentionally or unintentionally. In other words, present ideas in series, not in parallel.

— Me@2013-10-23 01:48:22 PM

The German philosopher G. W. F. Hegel wrote that any philosopher who uses the word “and” too often cannot be a good philosopher.

— Advice for the Young Scientist

— John Baez

2014.06.05 Thursday (c) All rights reserved by ACHK

長頸豹 3

尋找時間的定義 1.2

SICM, 3.2 | SICP, 2.2

這段改編自 2010 年 4 月 10 日的對話。



估不到,在大概 2006 年,我從一本電腦界的神作中,得到了靈感,開始對「時間定義」有一點理解。然後在今年(2010),再加上我在大學時代時,長期訓練得來的「語理分析」功力,我破解了,「時間」的大部分意思。





— Me@2014.06.03

2014.06.03 Tuesday (c) All rights reserved by ACHK

99% is no real certainty

Dear Giotis, they were formally at least 99.9999999% certain, that’s what the 6-7 sigma confidence level means, and even when some possible “qualitatively different errors” are considered as possibilities, their certainty is still vastly higher than 99%.

As I wrote in an update, Pryke of BICEP2 says that the rumors about the planned retractions by BICEP are pure bullshit.

99% is no real certainty. It’s just a laymen’s myth that 99% is high enough to treat something as a certainty. It’s less than 2 sigma. In hard sciences, if something comes out to confirm a theory at a 99% level, a scientist doesn’t consider it even as significant evidence to be carefully studied!

— Lubos Motl

This file is licensed under the Creative Commons Attribution 2.5 Generic license. Author: Mwtoews

In statistics, the 68–95–99.7 rule, also known as the three-sigma rule or empirical rule, states that nearly all values lie within three standard deviations of the mean in a normal distribution.

68.27% of the values lie within one standard deviation of the mean. Similarly, 95.45% of the values lie within two standard deviations of the mean. Nearly all (99.73%) of the values lie within three standard deviations of the mean.

— Wikipedia on 68–95–99.7 rule

2014.06.03 Tuesday ACHK

The Magic City


The second theme is concerned explicitly with technology. It is a law of life in the magic city that if you wish for anything you can have it. But with this law goes a special rule about machines. If anyone wishes for a piece of machinery, he is compelled to keep it and go on using it for the rest of his life.

– Disturbing the Universe, p.4




2009.12.21 Monday ACHK